To successfully connect your PrestaShop cart to ShipStation, first log in to your PrestaShop admin panel.
Here, you'll click Advanced Parameters and select Webservices from the dropdown.
At the top of this page, click Generate! to have PrestaShop generate a new ShipStation Access Key. In the Key description field, enter a name that pertains to this key, naming it "ShipStation Access Key" is suggested. (*Be sure to copy the Key value.)
Next, be sure Status is toggled to Yes.
Scroll down to the Resource table and check the Select All box for View (GET).
Now check the Modify (PUT) checkbox for order_carriers and orders and click Save.
After your changes have been saved, toggle Yes for Enable PrestaShop's webservice.
After this is configured, head to your Configuration Information under the Advanced Parameters dropdown.
In the upper righthand side of the page that appears, copy the Shop URL.
Once you have this Shop URL and Access Key, you're ready to plug these into ShipStation.
Head to your Account Settings (the wrench icon in the upper right).
Next, select Selling Channels and then Store Setup from the sidebar on the left.
Now, click + Connect a Store or Marketplace.
Select PrestaShop from the options on the popup and scroll down to step 12. Here, you'll enter the Web Service Key and Store URL. By default, the default statuses will be displayed. If you have customized your order statuses, update them accordingly.
(*Note, if ShipStation has trouble authenticating with your server, you or your system admin may need to add a .htaccess file to your webservices directory. This file should contain the following rule):
RewriteRule .* - [E=HTTP_AUTHORIZATION:%